System and method for engineered ceramic packages for use in fluid treatment technologies

ABSTRACT

The present disclosure relates to a method for making a ceramic mini-tube configured for use in a fluid modification system. The method involves using an electrospinning system to receive a quantity of precursor solution. The electrospinning system creates an electric field which causes the precursor solution, when emitted, to be stretched into a fiber jet. The fiber jet is deposited on a collector resulting in a fiber mat. The fiber mat is removed from the collector, wherein the fiber mat is formed into a shape. The fiber mat is further processed so that the fiber mat retains a desired shape. A heat treatment operation is then performed to convert the fiber mat into a ceramic structure having the desired shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional and claims priority from U.S.application Ser. No. 16/799,493, filed Feb. 24, 2020, which is acontinuation of U.S. application Ser. No. 16/739,830, filed Jan. 10,2020, which in turn claims the benefit of U.S. Provisional ApplicationSer. No. 62/791,652, filed on Jan. 11, 2019. The entire disclosure ofeach of the above referenced applications is incorporated herein byreference into the present application.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under Contract No.DE-AC52-07NA27344 awarded by the United States Department of Energy. TheGovernment has certain rights in the invention.

FIELD

The present disclosure relates to a ceramic package for treatingdifferent types of fluids, and more particularly to fluid modificationsystems (e.g., filtering and/or reactor systems) for treating fluids,liquids or gases, which make use of fully or partially formed mediaelements, for example tubular media, with the media having a nanofibrousor nanoporous construction and prepared by methods such aselectrospinning, extrusion, casting, or additive manufacturing. Thesemethods allow for the variation of micro-porosity and macro-porosity inaddition to the nanostructure for improving performance.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

The advantage and application of polymer nanofibrous structures,including 3D structures, is rapidly accelerating as the technology tofabricate and collect nanofibers improves. However, there has alwaysbeen a lag, and slower pace, in ceramic nanofiber development because ofadditional challenges. There are shrinkage and potential embrittlementchallenges associated with the thermal treatments required to convertpre-ceramic precursors into ceramic. These challenges have proven to bea barrier to the development of larger membranes suitable for manypresent-day applications.

There are several well-known prior art technologies for treating liquidsand gases. The simplest method is mixing additives into the fluid usingbatch or flow reactors. Another method is to use a filter pack throughwhich fluid flows and interacts with the media inside the filter pack. Afirst type of media that can be used is a packed particle bed. Onespecific type of packed particle bed is activated carbon particlescommonly used for portable and household water purification, as oneexample. The performance of a filter pack with particle media depends onthe size of the particles used. This is because there is a trade-offbetween particle surface area that the fluid gets exposed to and thepressure drop of the fluid flowing through the filter pack. Porousparticles help mitigate the effects of this trade off.

The second type of media used in filter packs comprises closely-spacedparallel membranes or channels. In this case, the fluid is exposed tothe media by cross-flow or flow over the membrane surface rather thanthrough the membrane. Cross-flow reduces the pressure drop compared topermeating through the membrane. Catalytic converters used to removetoxic pollutants from the hot exhaust gases of automobiles into inertgases are one example of a gas treatment technology that utilizescross-flow to treat a fluid. The exhaust gas flow in the channels of aceramic monolith with a honeycomb structure and the channels are coatedwith ceramic particles that support and stabilize the precious metalcatalyst that converts the pollutant into inert gas.

Traditional High Efficiency Particulate Air (HEPA) filtration is an airtreatment technology for removing aerosol particles from an air stream.HEPA filters can remove 99.97% of particles that are 0.3 μm or larger.HEPA filters can therefore remove dust, allergens, and airborne bacteriaand viral organisms, and thus are especially useful for ventilation andparticulate removal from air or gas streams. In a nuclear setting, HEPAfilters are invaluable in preventing the release and spread ofradioactive particulates.

HEPA filters are typically made with non-woven polymer or glassmicrofibers formed into a large sheet, which forms a filter media. Thelarge sheet of filter media is corrugated and sealed in a filter housingto increase the surface area of the sheet in the filter withoutcompromising the oncoming airflow. The increased surface area of themedia relative to the cross-sectional area of the fluid flow streamreduces pressure drop, just like cross flow methodology described above,except that the gas must still pass through the filter media since thereis no path through the filter other than through the corrugated filtermedia. Oncoming particulates thus flow with the air through the filtermedia. The fibrous nature of the polymer or glass microfibers ensnaressome of the particles as they move about a “torturous path.” HEPAfilters are limited to use at relatively low temperatures becausecomponents, e.g., binders and the polymeric or fiberglass media degradesat elevated temperatures.

With HEPA filters there are at least three distinct methods by whichparticles are transported and interact with the glass fibers. The firstmethod is impaction, which is typical of large particles that cannotfollow the curving contours of the air flow. These particles travel on astraight path and collide with a fiber directly without following thequick turns performed by the airflow. This effect increases as forlarger particles, smaller fiber separations, and higher flow velocities.

The second method is interception, which is where particles flowingalong the air flow come into contact with a fiber. This occurs whendistance between the airflow and the surface of the fiber is smallerthan the radius of the particle. The third method is diffusion which isespecially common with extremely small particles. This occurs due to howmicroscopic particles interact with the nearby molecules. Theirmovements are defined by Brownian motion or random erratic movements ofmicroscopic particles in a fluid due to particle interactions. Whilethese microscopic particles follow the air flow, their randomzig-zagging movement increases the distance that the particles travelwhich increases the probability that these particles are stopped byimpaction or interception.

Porous ceramic candles form another filtration method. They may bepacked in a parallel array for use in hot gas treatment and have some ofthe same beneficial features of traditional HEPA filters. The candlesare tubes sealed on one end so that the gas must flow through the wallof the candle. The tubes are long to maximize the surface area andminimize pressure drop. The pressure drop is further reduced if the tubewall microstructure is microfibrous instead of partially sinteredparticles. The candle wall structure is sometimes an asymmetric membranethat improves the properties of the candle. An asymmetric membrane has athick support that provides the candle with sufficient strength andsupports a thin, high-performance membrane. Keeping the high-performancemembrane thin is essential for minimizing pressure drop, and thus tomaximize efficiency.

Ceramic whiskers or needles have also been embedded into non-wovenmicrofiber filter media to improve performance of the media. A prior artarrangement involving the direct deposition of non-woven nanofibersdirectly onto current air filters by electrospinning to supplementfiltration works well for polymer nanofibers, but does not work for mostceramic nanofibers because of the thermal treatment that is required,associated shrinkage, and lack of thermal stability of current airfilters.

Another known method of concurrently filtering particles and collectinggases describes a filtration system where a functionalized coating ormembrane is applied to open-ended ceramic tubes that are capped andsealed in a filter assembly, but also does not work for ceramicnanofibers prepared directly from electrospinning because of the thermaltreatment, associated shrinkage, and potential embrittlement of themembrane.

At least one patent publication, U.S. 2010/0233812 A1, involves thesynthesis of titania ceramic membranes using a hydrothermal synthesisprocess. The process is similar to methods of making paper: fibers aredispersed in a solution to make a pulp followed by vacuum filtration ofthe pulp to form a cake on a porous substrate, which is then dried andthen heat treated. A macro-scale tube was prepared by this method as anexample of a shape that could be made, without describing ordemonstrating the utility of such a tube. The scale of the tube is alsonot addressed.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one aspect the present disclosure relates to a method for making aceramic mini-tube configured for use in a fluid modification system. Themethod may initially comprise providing a quantity of precursorsolution. The method may further comprise using the precursor solutionto form a fibrous structure which forms a mini-tube structure with anoverall configuration being at least one of toroidal or tubular. Themethod may further include processing the mini-tube structure using aheat treatment operation to covert the fibrous structure into theceramic mini-tube.

In another aspect the present disclosure relates to a method for makinga ceramic mini-tube configured for use in a fluid modification system.The method initially comprises using an electrospinning system toreceive a quantity of precursor solution. The method further comprisesusing the electrospinning system to create an electric field whichcauses the precursor solution, when emitted, to be stretched into afiber jet. The method further comprises depositing the fiber jet on acollector resulting in a fiber mat made up of pre-ceramic nanofibers.The method further comprises removing the fiber mat from the collector,wherein the fiber mat is formed into a shape, and then furtherprocessing the fiber mat so that the fiber mat retains a desired shape.The method further comprises performing a heat treatment operation toconvert the fiber mat into a ceramic structure having the desired shape.

In still another aspect the present disclosure relates to a method formaking a ceramic mini-tube configured for use in a fluid modificationsystem. The method comprises initially using an electrospinning systemto receive a quantity of precursor solution. The method furthercomprises using the electrospinning system to create an electric fieldwhich causes the precursor solution, when emitted, to be stretched intoa fiber jet. The method further comprises depositing the fiber jet on arotating collector resulting in a fiber mat. The method furthercomprises removing the fiber mat from the collector, wherein the fibermat is formed into a toroidal shape, and then further processing thefiber mat so that the fiber mat retains the toroidal shape. The methodfurther comprises performing a heat treatment operation to convert thefiber mat into a ceramic mini-tube having the toroidal shape, andwherein the ceramic mini-tube comprises a diameter of at least about 1mm.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure. Correspondingreference numerals indicate corresponding parts throughout the severalviews of the drawings, in which:

FIG. 1 is an illustration of one embodiment of a mini-tubular mediaconstruction with a nanofibrous or nanoporous microstructure prepared byelectrospinning, extrusion, casting, and/or additive manufacturing(e.g., 3D printing) in accordance with one embodiment of the presentdisclosure, which may be used to construct a fluid modification pack(pack), hereafter referred to as the “filter pack,” in accordance withone embodiment of the present disclosure;

FIG. 2 illustrates one shape, that being cylindrical, that the mini-tubemedia (which may be for treatment or filtration) of the presentdisclosure and that may have nanofibrous or nanoporous microstructure,and can be prepared by methods such as electrospinning, extrusion,casting, and/or additive manufacturing (e.g., 3D printing);

FIG. 3 illustrates another shape, that being toroidal, that themini-tube media of the present disclosure and that may be of nanofibrousor nanoporous microstructure and prepared by methods such aselectrospinning, extrusion, casting, and/or additive manufacturing(e.g., 3D printing);

FIG. 4 illustrates an end view of yet another form that the mini-tubemedia may take, that being a rolled element, and the rolled element mayhave a nanofibrous or nanoporous microstructure and prepared by suchmethods as electrospinning, extrusion, casting, and/or additivemanufacturing (e.g., 3D printing);

FIG. 5 shows a simplified illustration of the nanofibrous constructionof one of the toroidal mini-tubes of the present disclosure that has awall made out of nanofibers and has a hollow core;

FIG. 6a shows a side view of one of the toroidal mini-tubes of thepresent disclosure illustrating flow through the full thickness of themini-tube wall structure (i.e., through the membrane), and the mini-tubemay have a nanofibrous or nanoporous microstructure and prepared bymethods such as electrospinning, extrusion, casting, and/or additivemanufacturing (e.g., 3D printing);

FIG. 6b shows a side view of the toroidal mini-tube of FIG. 6a butillustrating a contact filtration flow path where the flow is over, andin contact with, an inner surface of the wall structure inside thehollow core of the mini-tube, and the mini-tube may have a nanofibrousor nanoporous microstructure and prepared by methods such aselectrospinning, extrusion, casting, and/or additive manufacturing(e.g., 3D printing);

FIG. 7 is a simplified illustration of a collection of toroidalmini-tubes of the present disclosure illustrating how both membrane andcontact flows occur, along with the formation of eddy flows thattypically occur when a plurality of the mini-tubes are packed in randomorientations, the mini-tube may have nanofibrous or nanoporousmicrostructure and prepared by methods such as electrospinning,extrusion, casting, and/or additive manufacturing (e.g., 3D printing);

FIG. 8 shows a graph illustrating how the toroidal mini-tubes of thepresent disclosure produce a notable reduction in pressure drop (“dP”)when compared to flow through a membrane of a support surrogatestructure with a coarse microstructure and with the same total surfacearea;

FIG. 9 shows a graph illustrating how the toroidal mini-tubes of thepresent disclosure produce a dramatic reduction in pressure drop ascompared to flow through a membrane of a HEPA surrogate with finemicrostructure and with the same total surface area;

FIG. 9a shows graphs of MTC filter efficiency comprising test resultscollected at 0.5 inch depth of filtration, along with projections thatsuggest at least a 6 inch depth of filtration can potentially result inHEPA quality filtration;

FIG. 10 is a picture of pre-ceramic toroidal mini-tubes in accordancewith the present disclosure produced using an electrospinning process;

FIG. 11 shows a highly enlarged illustration of the nanofibrousstructure of one of the toroidal mini-tubes of FIG. 10;

FIG. 12 shows another embodiment of the present disclosure whichinvolves a modular fluid modification system having a plurality ofnon-randomly oriented and independently manufactured components orelements (which may include treatment, filtering, and/or sensors) heldadjacent one another within a housing in desired angular orientationsrelative to one another, and furthermore which shows a nanofibrous ornanoporous media supported on a support structure (which may be producedby another method, e.g., electrospinning, casting, extrusion, oradditive manufacturing);

FIG. 13 shows another embodiment of the non-random elements in whichthere are circular openings with a selected degree of offset betweeneach element; and

FIG. 14 shows still another embodiment of the non-random elements inwhich triangular shaped openings are used with a selected degree ofoffset.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The present system and method relates broadly to a system havingrandomly orientated nanofibrous or nanoporous mini-structures ormini-elements that enable flow both through and along the wallstructures of the element. Merely for convenience, these mini-structuresor mini-elements will be referred to in the following discussion as“mini-tubes.” In one embodiment the mini-tubes have a toroidal ortubular construction, and each having a nanofibrous or nanoporousmicrostructure and that can be prepared by methods such aselectrospinning, extrusion, casting, and/or additive manufacturing(e.g., 3D printing). It will be appreciated, however, that while thefollowing discussion refers to “mini-tubes”, “toroidal mini-tubes” orother shapes for the mini-tube media, the mini-tubes do not have to beperfectly formed tubes. The mini-tubular media, or tube, can be toroidalor virtually any other shape and does not have to be a fully formed tubeor a fully closed tube. Still further, while a “tube” or “tubular”structure may be generally understood as having a length which isgreater than its cross-sectional dimension, and with a centrally locatedopening extending through its entire length, the mini-tubes of thepresent disclosure are not so limited. The term “mini-tube” as usedherein is intended to encompass structures with length/cross-sectionalratios more like a doughnut, but which still provide an internal flowpath through at least a portion of the overall length, as well aspermitting flow through a wall structure thereof. The internal flow pathneed not be perfectly linear, but could form a tortuous path, and mayextend fully through the entire length of the mini-tube, or may extendthrough only a portion of the overall length of the mini-tube. Thevarious embodiments of the mini-tube as described herein may be formedwith a spiral configuration, as a spiral, star, hexagonal, as adoughnut, as a corrugated element, or even as a gyroid element (e.g., atriply periodic minimal surface structure), or with virtually any othershape. Alternative shapes can be intentionally used to impart a desiredmacro porosity in addition to the nanofibrous or nanoporousmicrostructure. Likewise, the microstructure can include microporosityin the microstructure in addition to the nanofibrous or nanoporousmicrostructure construction. Also, while random orientations of themini-tube elements are discussed herein, non-random or orderedorientations and assemblies of the mini-tube elements are just aspossible as well, along with possibly a mixture of ordered and randomlyorientated mini-tube elements.

Referring to FIG. 1, one embodiment of a fluid modification system 10forming a pack in accordance with the present disclosure is shown. Whilethe fluid modification system 10 may be used in applications forperforming fluid treatment and/or fluid filtering operations, as willbecome more apparent from the following discussion, for convenience thesystem 10 will be referred to hereinafter simply as “the filter pack”10, with it being appreciated that the functionality of the filter pack10 is not restricted only to filtration applications.

It will also be appreciated that the term “fluid” as used in thefollowing discussion may encompass any flowable medium, for exampleliquids or gases, including and without limitation air, gases, mixturesof non-air gases and air, water, petroleum, oil, chemical feedstock,drugs, etc. Moreover, the fluids could be radioactive, hazardous, orvaluable fluids or contain radioactive, hazardous, or valuablematerials. The fluid modification capable of being performed by thevarious embodiments and methods described herein may involve changingthe physical, chemical or any other properties and characteristics ofthe fluid as it flows through the filter pack 10. Such changes may be byfiltration, size selection or segregation or discrimination, thermaltreatment, chemical treatment, (e.g., catalytic reaction), adsorption,absorption, “physisorption”, “chemisorption”, and adding or subtractingmaterial (e.g., particles or chemicals) to the flow stream. As such, thefluid modification media discussed herein can be adapted to perform anyof one or more fluid processing methods such as, without limitation,particulate filters (e.g., HEPA, ceramic, clean room, sub-HEPA orprocess filters), and also to perform fluid treatment using reactive orcatalytic materials.

The filter pack 10 may include a plurality of mini-tubes 12 randomlyorientated in a suitable container structure 14. The mini-tubes 12 arepreferably made from ceramic, and are sufficient in number such thatthey preferably fill the container structure 14 while being arranged inrandom orientations within the container. As such, a fluid flow 16 thatenters the filter pack 10 will flow 1) through at least a subpluralityof the porous, mini-tube wall structure 12 a, shown in FIG. 2, whenflowing completely through the container structure 14 (generallyunderstood as a “membrane-filtration or permeation”); as well as 2) overand around the exposed surfaces of mini-tubes 12 wall structure 12 a,and also over exposed exterior and interior surfaces of various ones ofthe mini-tubes 12 if the mini-tubes have a toroidal or hollow tubularshape, as will be discussed below. In either event, the fluid flow 16will flow through and around a plurality of the mini-tubes 12 whenflowing completely through the container 14 (generally understood as“contact” filtration or flow, where contact filtration with exposedinner and/or outer surfaces of the mini-tube wall structures occurs);and 3) as well as in combinations of flow paths randomly both throughand over inner and outer surfaces of the wall structure 12 a variousones of the mini-tubes 12.

The container structure 14 may be formed of any suitable material, forexample ceramic, glass, plastic, metal, etc. The container structure 14,while shown as having a generally square shape in FIG. 1, may berectangular, cylindrical, spiral, star, hexagonal, or of any other crosssectional shape. The container structure 14 may have a length whichforms a linear flow path, a non-linear flow path, a serpentine flowpath, or virtually any other configuration, and the present disclosureis not limited to use of a container having any particular crosssectional shape or any type of configuration. The only requirements forthe container structure 14 is that its input side 14 a and output side14 b be constructed of a material, for example ceramic, glass, plastic,or metal, which permits a flow therethrough of the flowable medium beingtreated or filtered, while still being able to prevent the mini-tubes 12from spilling out of the container structure. The container structure 14may be made by any suitable method, but one specific method may be byadditive manufacturing. For example, as a way to overcome manufacturingchallenges of joining different parts of the container structure 14, 3Dprinting may be used to print the walls and floor of the containerstructure 14 together rather than welding or affixing them withfasteners or adhesives.

FIGS. 2-4 illustrate some examples of the different shapes that themini-tubes 12 may take. The mini-tubes 12 are preferably made fromceramic and form a central feature of the present disclosure. Theceramics have nanofibrous or nanoporous microstructure and are preparedby methods such as, without limitation, electrospinning, extrusion,casting, and/or additive manufacturing (e.g., 3D printing). Ceramics mayinclude oxides or non-oxide ceramics. Oxide ceramics and non-oxideceramics may have insulating or conducting properties. The ceramic maybe a catalyst. The ceramic may support a catalyst or reactant. Catalystson the surfaces of the ceramic may include precious metal catalysts.Catalysts on the surfaces may be transition metal catalysts. Catalystson the surface may be ceramic catalysts. Accordingly, at least some, orpossibly all, of the mini-tubes 12 may have nanofibers with afunctionalized surface, either due to the intrinsic functionality of thesurface or due to extrinsic functionality added to the surface. In oneembodiment the functionalized surface may be functionalized to support acatalyst. In one embodiment the functionalized surface is functionalizedto capture an analyte. The mini tubes 12, 12′ and 12″ disclosed in FIGS.2, 3 and 4, respectively, could also be made with glasses or metals.

While FIGS. 2, 3 and 4 illustrate specific examples of the shapes thatthe mini-tubes 12 may take, the construction of the mini-tubes is notlimited to any one particular shape or configuration. FIG. 2 shows oneof the mini-tubes 12 forming a hollow cylindrical component having anexterior wall surface 12 a, while FIG. 3 shows a mini-tube 12′ forming atoroidal element having a wall portion with both an exterior outer wallsurface 12 a′ (representing a nominal inner diameter) and exterior innerwall surface 12 b′ (representing a nominal outer diameter), and wherenanofibrous material of the wall portion may be partially randomlyoriented or fully randomly oriented. FIG. 4 shows a mini-tube 12″ havinga rolled construction. Combinations of two or more different shapes ofthe mini-tubes 12 may also be used to form the filter pack 10, anddifferent segments of the filter pack 10 could include different shapesof the mini-tubes 12. The mini-tubes 12 may also be formed withdifferent lengths or cross-sectional dimensions and intermixed into thecontainer structure 14. The mini-tubes 12 may also be of differentmaterial construction, sizes, shapes, and intermixed combinations ofthese previously described elements in a variety of ratios into thecontainer structure based on properties that can be known to thoseskilled in the art of filtration, catalysis, or separations 14.

The creation of the ceramic mini-tubes 12 solves the shrinkage challengethat has been a longstanding challenge when attempting to form a filtermedia using ceramic nanofiber membranes. The mini-tubes 12 form aself-supporting geometry that can shrink freely during manufacture,without the constraint of a substrate that may cause tearing orcracking. The mini-tubes 12 also have better strength compared to aconventional membrane because of their geometry. In one embodiment themini-tubes 12 may have a ring or toroidal structure such as that shownin FIG. 3, but which has been rolled, such as shown in FIG. 4. Therolled construction allows for even higher stresses before failureoccurs. Compression is the most likely stress applicable to the ceramicmini-tube 12, whereas bending is the most likely stress applicable to aceramic membrane if it is not supported on a substrate. Toroidal orother structures can be expected to impart greater compressive strengthto the mini-tubes. It will also be appreciated that the compressionstrength of ceramics is systematically higher than the bending strength.The invention of the ceramic mini-tubes 12 solves the scaling tomanufacturing challenge by scaling quantity (i.e., the number ofindividual mini-tubes 12 instead of the overall size and length of themedia). The ceramic mini-tubes 12 can be of nanofibrous or nanoporousconstruction and prepared by methods including, but not necessarilylimited to, electrospinning, extrusion, casting, and/or additivemanufacturing (e.g., 3D printing).

Referring to FIG. 5, a highly magnified illustration of one of themini-tubes 12 can be seen. The wall construction of the mini-tube 12 ismade up of a large plurality of unwoven, arbitrarily orientednanofibrous strands or fibers 18. The nanofibers 18 may also be in analigned orientation.

FIGS. 6a and 6b depict the two different types of flow mechanismsthrough the mini tubes 12 in filter pack 10. FIG. 6a shows membranepermeation flow in which the fluid (e.g., air flow) 16 flows through theporous wall 12 a of the mini-tube 12. FIG. 6b shows a contact flow wherethe fluid flow 16 flows over and in contact with the exterior and/orinner wall surface of the mini-tube 12. A hollow structure is animportant feature that reduces pressure drop as demonstrated in FIG. 8and FIG. 9.

FIG. 7 shows a further illustration of three distinct possible flowpaths through the filter pack 10 mentioned above, where dots 20 and 22represent a specific point in a cross section of the filter pack 10. Thefirst flow path 24 represents fluid (e.g., air) flow 16 travellingthrough the mini-tube 12 porous wall at dot 20. The second flow path 28illustrates fluid (e.g., air) flow 16 travelling through the hollow coreof mini-tube 12 at dot 22, resulting in contact filtration. Acombination of flow through the mini-tube 12 porous wall and contactflows at the same cross-section of the filter pack 10 provides asignificant benefit in reducing the pressure drop (“dP”) experienced bythe fluid (e.g., air) flow. The third flow path 26 shows a contact flowextending over an inner surface of one of the mini tubes 12 because of aflow eddy caused by local pressure gradients that enhances the filteringaction of the mini-tubes 12 on the fluid (e.g., air) flow 16. Becausethe third flow path 26 still traverses a mini-tube 12 porous wall, thismovement over and in contact with the wall of the mini-tube 12 providesa filtering action on the air flow without creating a significantpressure drop on the air flow.

While the mixed filtration represented by the first flow path 24 andsecond flow path 28 does introduce a pressure drop on the airflow, thehierarchical architectures that make up each of the mini-tubes 12 stillenables the pressure drop to be dramatically reduced as compared withother types of membrane-like treatment media or filter media. Testresults obtained by the co-inventors have demonstrated that using themini-tubes 12 as filtration media in a flow stream reduced the pressuredrop by an order of magnitude or more when compared to the pressure dropthrough a membrane of equivalent mass and surface area. This isillustrated in FIGS. 8 and 9. In FIG. 8, it can be seen that themini-tubes 12 provide a significant reduction in pressure drop,represented by curve 52, when compared to a pressure drop of a membrane,represented by curve 50, for a support surrogate material having arelatively coarse microstructure. FIG. 9 shows the pressure drop of aHEPA filtration media surrogate in membrane form 54 with finemicrostructure as compared to the mini-tubes 12 having a finemicrostructure, represented by curve 56. Particularly in FIG. 9, it willbe noted that the reduction in pressure drop produced by the mini-tubes12 is on the order of about 1000 times that of the HEPA surrogate withfine microstructure at most flow rates.

In one real world application, for example retrofitting new filtertechnology into U.S. Department of Energy (DOE) nuclear facilitiesrequires dP comparable to the current filters, which the ventilationsystems were designed to accommodate. The mini-tubes 12 meet the targetdP performance (≤1 “H₂O below 170 L/min in the allotted test volume),whereas the membranes filters do not. It is important to note thatexisting DOE nuclear, radiological, and biological facilities containventilation systems that utilize specific size filters. Filter packsmade of elements (e.g., mini-tubes) can be made to fit into thesespecific sizes, thereby meeting spatial retrofitting requirements. Otherapproaches that do meet these spatial and dP requirements could requirecost and schedule prohibitive modifications to existing DOE facilities.In FIG. 9a , a preliminary filter efficiency measurement made using a0.5 inch depth of filtration (DOF) resulted in 50% removal efficiency ofa dioctyl phthalate (DOP) aerosol. Assuming each additional 0.5 inch DOFremoves 50% of the remaining DOP aerosol suggests that a DOF of at least6 inches is required to remove 99.97% of the DOP aerosol and has thepotential to fit within the spatial retrofitting requirements for HEPAfilters.

It will be appreciated that the mixed-filtration mechanisms representedby flow path 28 (FIG. 7), as well as the dimensions of the mini tubes12, can affect the filtration efficiency as well as the dP. Accordingly,these factors will need to be taken into consideration by the designerin balancing filtration efficiency with the minimum desired pressuredrop.

The present disclosure also discloses a new process for fabricatingceramic mini-tubes 12. Manufacturing of the ceramic mini-tubes 12 may beaccomplished through the use of an electrospinning system, for example,but not limited to, the Fluidnatek LE10 system available from BioiniciaSL of Valencia, Spain, which may consist of a spinneret, where aprecursor solution is emitted and becomes stretched into a fiber jet byan electric field. The fibers are deposited on a collector, which in oneexample may be a rotating mandrel, or optionally a rotating drum, oroptionally a stationary flat plate. For convenience, the collector willbe referred to in the following discussion as the “rotating mandrel” orsimply “mandrel”. The fibers are then removed as a fiber mat from themandrel and formed into a shape to create the pre-ceramic mini-tubes 60as shown in FIG. 10. The pre-ceramic mini-tubes 60 have a wall made ofnanofibers 60 a with textured microporosity and loaded with ceramicprecursors, as better seen in FIG. 11. These nanofibers 18 (FIG. 5) and60 a (FIG. 11) typically may have a diameter in the range of 50 nm-200nm. The fibers shrink during the ceramic conversion process (i.e.,thermal treatment) and the ceramic nanofibers typically have a finaldiameter in the range of 50-100 nm. In this example, the ceramicmini-tubes 60 have a diameter of about 1-2 mm, a length of about 1.0-1.5mm, a wall thickness of about 100 μm, pores about 1 μm in size, and ananofiber structure with fiber diameters near 100 nm. These exampledimensions apply as well to the various examples of the ceramicmini-tubes 12, 12′ and 12″ described in connection with FIGS. 2-4. Thesize features (ranging from 1 mm to 100 nm) cover five orders ofmagnitude. The co-inventors believe that an even more thoroughunderstanding as to how filtration performance—dP and filtrationefficiency—is affected by independent control of these differentdimensional scales, may likely be gained with further research andexperimentation. It will also be appreciated that the nanofibers canstay precursors and don't always have to be converted to a ceramic.Furthermore, the mandrel or mat may have a coating or layer (e.g., mylarsheet) that helps act as a release agent.

The manufacture of the mini-tubes 12 is not limited to electrospinning,but may also be achieved through extruding, casting, and/or additivemanufacturing (e.g., projection microstereo-lithography (PpSL), anddirect ink writing (DIW) (two forms of 3D printing). Furthermore,sacrificial template printing may also be used to help construct themini-tubes 12. Sacrificial template printing is an additivemanufacturing technique wherein an organic (e.g., polymer, resin)additive manufactured part is coated with a ceramic (e.g., dip-coating,plasma deposition, etc.) and then heat treated to fully or partiallyremove the organic.

The extrusion and casting methods of making the mini-tubes 12 areparticularly advantageous as they represent existing commercialtechnology for ceramic manufacturing. With any of the above enumeratedmanufacturing approaches, the feedstock needs to be compatible with theselected approach. Direct ink writing (“DIW”) is an additivemanufacturing technique that facilitates customizable geometric designand enables the construction of the mini-tubes 12 as non-axisymmetricfiltration media, which could be helpful for controlling the flow paththrough the filtration media. The electrospinning process discussedabove produces a different hierarchical architecture (nanofibers createmicroporous channels), which can increase flow through the walls of thefiltration media and thereby improve filtration efficiency.

It will also be appreciated that the term “ceramic” as used herein maymean “ceramic and/or ceramic composite” for the purposes of the presentdiscussion. For example, using sacrificial 3D printing can leave someorganic behind.

Important specific advantages of the present disclosure include thevariety of different ceramic mini-tubes 12 that can be implemented intothe filter pack 10, the useful properties of ceramics, the extremelyhigh surface-to-volume ratio of the ceramic nanofibers 18 used toconstruct the mini-tubes 12, and the low pressure drop through thefilter pack 10. The nanofiber forming process depends primarily on thepolymer precursors rather than the ceramic precursors. Thus, a varietyof ceramic precursors can be used in the process to synthesize a varietyof ceramics. This enables tailoring the unique chemical, thermal,electrical, magnetic, and optical properties of the ceramic nanofibersfor different applications of interest. The extremely highsurface-to-volume ratio of ceramic nanofibers enables exposure to highersurface areas in a smaller volume, which is potentially useful forapplications with physical space restrictions or that requires smalltreatment or filtering modules. The low pressure drop through theceramic nanofiber media also ensure high energy efficiency associatedwith flowing fluid through the filter pack 10.

The geometry of the mini-tubes 12 is known to reduce pressure drop (dP)when compared to flow-through membranes of equivalent mass and surfacearea. This is evidenced by the graphs of FIGS. 8 and 9. A reduced dPfacilitates retrofitting advanced filter packs 10 into existing systemsand facilities, for example into U.S. Department of Energy facilities,to make them even safer while simultaneously reducing operational costs.The operation of a ventilation system is a key cost driver for manyindustries, and particularly with U.S. Department of Energy nuclearfacilities. Reducing dP can significantly reduce the operational costsof an entity. Filter designs that can accommodate the same flow andpressure drop characteristics in a filter form factor that matchesexisting or established filter sizes provides for a significant costsavings in retrofitting improved mini-tube based filter technologiesinto the extensive quantity of existing buildings utilizing existingfilter technology.

Another significant advantage of the ceramic mini-tubes 12, whenconstructed using electrospinning, is that the ceramic mini-tubes arethermally stable up to 850° C., or even higher temperatures depending onthe ceramic material. This may lessen the need for elaborate firesuppression systems in some environments. It is well known thatconventional HEPA filters using polymers for the filter medium, as wellas in binders and seals, are highly susceptible to elevated temperature,fire and water damage, thus necessitating expensive installation,monitoring and maintenance of fire suppression systems to protect HEPAfilters. Similarly, metal separators typically used in conventional HEPAfiltering systems are susceptible to corrosion. Furthermore, disposalcosts are a function of the lifetime of a filter, which may in turn beaffected by exposure to moisture and/or corrosives. These drawbacks arenot present with a ceramic filter pack 10 of the present disclosure.

Another embodiment is use of mini-tube sensors in the ceramic package.The nanofibrous mini-tube may be constructed of nanofiber sensors inindividual strands of nanofiber sensors, or all strands includenanofiber sensors. The sensor could be made from any plurality of minitubes. Different types of mini tube sensors may be included in theceramic package. The sensors may provide feedback on the performance ofthe ceramic package or on analytes in the flow stream. Other ceramicsensor materials not made from nanofibers may also be included in theceramic package.

Modular Ceramic Multi-Function Fluid Treatment Systems

In additional embodiments, the present disclosure further relates toembodiments of modular, ceramic multi-function fluid treatment systemsand constructions. In these embodiments the ceramic substrates may havea specific macrostructure, microstructure, nanostructure, reactant,catalyst, and/or arrangement to control functionality of the substrate.Such functionality may include filtering, treating (e.g., with reactantsand/or catalysts), intentionally directed flow paths, pressure dropcontrol, adsorption and absorption capacity, mechanical support for thinceramic membranes or multi-functional material properties, for example.Functionality also includes controlled shrinkage characteristics duringa thermal cycle, which facilitates integrating a plurality of componentsin a modular fluid treatment configuration. Functionality may includethe use of surface modifications that change the function of thesurface, such as creating bonding or attachment sites for specificity orspecific adsorption of a target material relative to other materials.

The various embodiments to be discussed below were invented in responseto challenges in two different areas and combine the benefits of two ormore manufacturing approaches. The challenges include 1) constrainedshrinkage of ceramic nanofibers prepared by electrospinning that causethem to tear or break and 2) size/resolution and speed trade-offs andlimitations of additive manufacturing. The present disclosure thereforerelates to the synergistic use of electrospinning, additivemanufacturing, and conventional processing together to construct fluidtreatment systems and filters that mitigate challenges associated withthe individual approaches, but that also add valuable functionalitybased on the benefits of each approach. Also realizing that scaling sizeof additively manufactured parts is often a challenge, the modular fluidtreatment and filter systems of the present disclosure enable scaling ofquantity to create systems having desired capabilities, as compared todirectly scaling size in one single fluid treatment or filteringelement. Functionality may include the use of surface modifications thatchange the function of the surface, such as creating bonding orattachment sites for specificity or specific adsorption of a targetmaterial relative to other materials.

The various embodiments discussed below are based on mesh-like orlattice-like substrates with a variety of mesh or lattice structures.These substrates can be, for example, polymer or polymer ceramiccomposites. Polymer substrates (e.g., produced by 3D printing) may bepost-processed (e.g., coated with a ceramic slurry or plasma coated).Thermal treatments can be used to partially or fully decompose polymersin ceramic coated polymers or polymer/ceramic composites so that theybecome ceramic only. The ceramic may be partially sintered so that itretains a porous microstructure. The substrates may be coated withpolymer nanofibers that contain ceramic precursors. One example afterheat treatment is a mesh with porous ceramic struts that are also hollowwhere the polymer strut has been removed to reduce resistance to flowwhen integrated into a filter. Thermal treatments can convert thesubstrate and nanofibers to ceramic. The shrinkage of the substrate canbe matched to the shrinkage of the nanofibers so that stress does notbreak the nanofiber coating. The meshes can be stacked, for example, ina tube to create a modular fluid treatment system or modular filtersystem. The meshes can be rotated relative to each other to control flowpaths once stacked. The meshes can be tiled into larger panels ofvirtually any cross sectional size. These panels may be placed in acorrugated configuration or stacked to create a modular system of widelyvarying dimensions to meet the needs of a particular application. Themeshes in a modular fluid treatment system or modular filter system canbe all of the same type or they can be any number of different types.

While various types of printers may be utilized to construct theembodiments discussed herein, one particular 3D printer that is expectedto prove valuable is the Connex 3 Object260 printer available fromStratsys of Eden Prairie, Minn. This printer can provide layerresolution from about 16-32 μm. However, the embodiments of the presentdisclosure are not limited to the production from only this specificmodel/make of printer, and it will be appreciated that other 3D printersmay also prove suitable for the manufacture of the embodiments discussedherein.

One embodiment of a new modular layered fluid treatment system 100 inaccordance with the present disclosure is shown in FIG. 12. The system100 in this example comprises an outer tube 102, in this example acylindrical tube, which houses a plurality of independent, disc-likefluid contacting elements 104, 106, 108, 110, 112 114 within the outertube 102. For ease in illustrating and explaining the system 100, theouter tube 102 is shown transparently to illustrate the positioning ofthe fluid contacting elements 106-114 within the outer tube.

The outer tube 102 may include a cover or flange 116 at each end (onlyone being shown in FIG. 12) to retain the fluid contacting elementstherein without impeding fluid flow into or out from the system 100. Theouter tube 102 may be made from ceramic, metal, plastic or any othersuitable material which is impervious to the fluid flowing through thesystem 100. While the outer tube 102 is shown having a cylindricalshape, the system 100 is not limited to this cross sectional shape, andin fact may use outer tubes having square, rectangular, pyramidal,hexagonal, pentagonal, or virtually any other cross sectional shape thatmeets the needs of a specific application. The overall length of theouter tube 102 and the number of independent fluid contacting elementshoused therein will have a bearing on the efficiency and pressure dropthat the fluid flow experiences, and as such these are designconstraints that will be dictated by the needs of specific applications.

In the example of FIG. 12, the fluid contacting elements 104-114 areconstructed generally identically to have a solid, impervious to fluidflow, outer frame portion 118, and a grid like structure ofperpendicularly oriented wall portions 120 which define a plurality ofsmall, square-shaped openings 122. The wall portions 120 may be formed(e.g., by 3D printing or other methods) to have a porous construction toincrease the surface area of the fluid contacting element. It will beappreciated that the shape of the openings 122 need not be squareshaped, and the precise shape of the openings 122 will depend on the howthe wall portions 120 are arranged. Further, the wall portions 120 canbe orientated parallel to the direction of fluid flow (defined by arrow“A”) through the openings 122, or instead the wall portions 120 may beangled slightly non-parallel to the direction of fluid flow to increasethe degree of impaction of particles entrained in a fluid with the wallportions 120 as the fluid flows through the fluid contacting element104.

The openings 122 of each fluid contacting element 104-114 collectivelyform an orderly, grid-like arrangement of fluid flow paths which allow afluid flow to pass through each of the fluid contacting elements104-114. The dimensions of the openings 122 may vary considerably, buttypically may be formed, for example, by using a suitable 3D printerwith squares having dimensions on the order of 1-2 mm×1-2 mm or smaller,and a separation thickness (i.e., defined by walls 120 thickness) of 1mm-2 mm or smaller. The resolution of the openings 122 may be limited bythe particular printer or manufacturing technique used, as well as otherfactors. The size of the openings 122 and the thickness and porosity ofthe wall portions 120, which together control the surface area that thefluid flow “sees” as it flows through each fluid contacting element104-114, will have a significant influence on the pressure dropexperienced by a fluid flowing through the filter system 100.Accordingly, these are design variables that the designer needs toconsider for each application.

The overall thickness of each fluid contacting element 104-114 may varyto suit the needs of a specific application, but may typically be about1-10 mm, but as one specific example the fluid contacting elements104-114 may each have a thickness of about 5 mm. As the fluid contactingelement 104-114 is made thinner and thinner, the risk of bending ordrooping of sections of the wall portions 120 may increase. And whilethe fluid contacting elements 104-114 are shown in FIG. 12 as all havingthe same overall thickness, with the same size openings 122 and the samewall 120 thicknesses, it will be appreciated that this is not absolutelynecessary; certain ones of the elements 104-114 may have a greater orlesser overall thickness, and/or sized openings 122, and/or wall portion120 thickness which is greater or lesser than the other ones of theelements. These variations may be used to control flow through thesystem 100 or for different filtration, separation, and/or reactionstages

Referring further to FIG. 12, the outer frame portion 118 can be seen toinclude a pair of shoulder portions 124 arranged to project in radiallyopposite directions from one another. The shoulder portions 124 areshaped to fit within corresponding channels 126 on an inside surface 102a of the outer tube 102 and to hold the fluid contacting elements104-114 against rotational movement once they are inserted in the outerhousing 102. Again, while two shoulder portions 124 and two channels 126are shown, the fluid contacting elements 104-114 could each beconstrained within the outer tube 102 using only a single shoulder 124and a single channel 126. Conversely, the shoulder portions 124 could beformed to project from the interior wall 102 a of the outer tube 102,while the fluid contacting elements 104-114 each include a selectivelyplaced, complementary shaped channel or groove to engage with theshoulder portions, to thus hold the elements in a desired angularorientation within the outer tube. In either event, once each of thefluid contacting elements 104, 106, 108, 110, 112 and 114 is insertedinto the outer housing 102, each is held in a specific angularorientation within the outer housing, and in a specific angularorientation relative to its adjacent element(s).

Referring further to FIG. 12, it can be seen that fluid contactingelement 106 includes wall portions 120 which are formed at a differentangular orientation than those of the element 104, relative to theorientation of its shoulder portions 124. Although the wall portions 120of fluid contacting element 108 are not visible in FIG. 12, its wallportions are also formed at a different angular orientation from fluidcontacting element 106. In one embodiment, the fluid contacting elements104-114 are each formed with a predetermined angular “offset”, forexample about 5°-15°, so that once assembled into the outer housing 102,the element 106 will be angularly offset by a predetermined amount fromthe element 104, the element 108 will be angularly offset by the sameamount from the element 106, and so forth for all the remaining fluidcontacting elements 110-114. The selected angular offset creates atortuous flow path throughout the system 100 and can be selected totailor the fluid treating (e.g., filtering) capability (i.e., degrees ofparticle impaction, interception and diffusion) experienced by theparticles, as well as the pressure drop of the system 100.

When laying out the grid pattern of the openings 122 in the fluidcontacting elements 104-114, it will also be preferable to arrange thewall portions 120 such that wall portions are not oriented around theaxial center of each element (i.e., such that a square shaped opening isnot formed at the axial center of each fluid contacting element104-114). This will eliminate creating a central opening straightthrough the entire length of the system 100.

Referring to FIG. 13, another embodiment of a fluid contacting element200 is shown which incorporates radially opposing shoulder portions 202,and circular shaped openings 204 formed through the thickness of a wall206 of the element 200. In this example the selected diameter of thecircular shaped openings 204 may vary as needed to meet a specificapplication, but it is expected that for many applications a diameter ofabout 1 mm-5 mm or smaller will be suitable. It will also be understoodthat FIG. 13 illustrates a plurality of fluid contacting elements 200stacked on top of one another. This creates openings 204 which areslightly angularly misaligned with one another, which has the effect ofcreating a continually helical flow vortex through the openings 204 whenthe elements 200 are installed adjacent one another in an outer tube,such as the outer tube 102 in FIG. 12. Again, the size of the circularopenings 204 and the degree of offset selected may be varied to suitspecific performance requirements. Preferably, the fluid contactingelements 200 are constructed so that each does not have a circularopening 204 at the axial center of the element, which avoids forming astraight path through all of the elements 200.

Referring further to FIG. 12, another embodiment may involve channelswith the elements 200 that make up the overall fluid treatment or filterpack. In this embodiment, the respective openings of consecutiveelements may be aligned to form channels that stay separate and/orintersect. Such channels may be lined with, composed of, or coated with,different catalysts or reactants.

FIG. 14 shows another embodiment of a fluid contacting element 300 ofthe present disclosure. The fluid contacting element 300 likewiseincludes shoulder portions 302 extending radially from one another, butinstead of circular openings 204, the element 300 includes a surface 306having triangular shaped openings 304. The triangular shaped openings304 of two or more of the fluid contacting elements 300 may likewise bemanufactured to be offset by a selected angle, which would createtriangular shaped openings having gradually changing dimensionsthroughout the length of a plurality of adjacently mounted fluidcontacting elements 300. The spacing of the triangular shaped openings304, as well as the dimensions of the openings, may be varied as neededto suit specific performance requirements, but in one specific examplethe spacing may be between about 0.2 mm-1 mm or smaller, while the threesides of each of the triangular shaped openings 304 may typically beabout 0.5 mm-4 mm in length or smaller.

While FIGS. 12-14 and the above discussion involve square, circular andpyramid shaped openings formed in the fluid contacting elements, it willbe appreciated that the openings are not limited to only these shapes.Other shapes, for example possibly hexagonal, pentagonal, octagonal,rectangular, oval, just to name a few, may be used to form the openingsin the fluid contacting elements. Even combinations of fluid contactingelements having different shaped and/or dimensioned openings may beused. A single element could also have a combination of openings withdifferent shapes and sizes.

The modular construction of the system 100 and the various embodimentsof the fluid contacting elements 106-144, 200 and 300 enable a fluidtreatment (e.g., filtering) system to be modularly constructed thatmeets a wide range of performance requirements, and which can be easilymodified if needed by adding, removing, or changing one or more fluidcontacting elements. Importantly, the modular construction of the system100, and the use of a plurality of fluid contacting elements, enablesthe manufacturing limitations of present day manufacturing systems(e.g., printing limitations of existing 3D printers) in producing largersizes to be overcome by using a plurality of adjacently placed smallerfluid contacting elements. Similarly, the limitations of existingmanufacturing approaches, including existing 3D printers, in printing orcreating a part having overall length and width, or overall diameterlimitations, may be overcome by using the above-described modularapproach.

While the foregoing discussion has used 3D printing as one method forconstructing the fluid contacting elements, it will be appreciated thatthe elements, as well as the outer tube for hold containing them, may bemade by other methods, for example and without limitation, by extrusion,casting and/or electrospinning techniques, or possibly even combinationsof these and other techniques.

The various embodiments of the fluid contacting elements describedabove, because of their modular construction, enable a wide variety ofgeometries to be formed besides just a tubular geometry shown in FIG.12. For example, the fluid contacting elements may be arranged adjacentto one another (i.e., “tiled”) in a common plane to form a much largerfluid contacting “sheet” that would otherwise not be capable ofmanufacture as a single unit because of present day limitations with 3Dprinting and other manufacturing techniques. The fluid contactingelements may also be stacked in different ways, or potentially arrangedin distinct groups within interconnected housings that form anon-straight flow path.

The various embodiments of the present disclosure are expected to findutility in a wide range of applications, not just limited to fluidfiltering applications, but potentially as fluid reactor systems aswell. The various embodiments are expected to be used in a wide varietyof settings such as industrial manufacturing facilities, assemblyplants, in nuclear and/or chemical facilities, in energy producingfacilities, possibly in urban environments such as in subway stations orlike areas where clean air is desired but where air circulation may belimited, at street level areas where air quality may be compromisedbecause of frequent vehicle traffic or other types of emissions fromnearby facilities, at firing ranges (e.g., for removal of airborne leadparticles), and in connection with water supplies that requirefiltration, just to name a few possible applications.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

1. A method for making a ceramic mini-tube configured for use in a fluidmodification system, the method comprising: providing a quantity ofprecursor solution; using the precursor solution to form a fibrousstructure which forms a mini-tube structure with an overallconfiguration being at least one of tubular or toroidal; and processingthe mini-tube structure using a heat treatment operation to covert thefibrous structure into the ceramic mini-tube.
 2. The method of claim 1,wherein using the precursor solution to form a fibrous structure whichforms a mini-tube structure comprises using an extrusion procedure toform the mini-tube structure.
 3. The method of claim 1, wherein usingthe precursor solution to form a fibrous structure which forms amini-tube structure comprises using an additive manufacturing process toform the mini-tube structure.
 4. The method of claim 1, wherein usingthe precursor solution to form a fibrous structure which forms amini-tube structure comprises using a casting process to form themini-tube structure.
 5. The method of claim 1, wherein the ceramicmini-tube includes at least one of a diameter of 1 mm-2 mm, or a lengthof about 1 mm-3 mm; or pores about 1 μm in size.
 6. A method for makinga ceramic mini-tube configured for use in a fluid modification system,the method comprising: using an electrospinning system to receive aquantity of precursor solution; using the electrospinning system tocreate an electric field which causes the precursor solution, whenemitted, to be stretched into a fiber jet; depositing the fiber jet on acollector resulting in a fiber mat made up of pre-ceramic nanofibers;removing the fiber mat from the collector, wherein the fiber mat isformed into a shape; further processing the fiber mat so that the fibermat retains a desired shape; and performing a heat treatment operationto convert the fiber mat into a ceramic structure having the desiredshape.
 7. The method of claim 6, wherein the processing of the fiber matincludes at least one of: utilizing heating of the fiber mat to causethe fiber mat to retain the desired shape; or applying adhesive bondingto the fiber mat to cause the fiber mat to retain the desired shape. 8.The method of claim 7, wherein depositing the fiber jet on a collectorproduces fibers having the following features: an average diameterbetween at least 100 nm; and a fiber mat thickness between 10 nm-400 μmor a fiber mat area density of between 1-100 g/m².
 9. The method ofclaim 6, wherein the collector comprises at least one of the followingcomponents, with or without a cover film or coating: a rotating mandrel;a rotating drum, or a stationary flat plate.
 10. The method of claim 9,wherein the collector comprises the rotating mandrel, and wherein themethod further comprises removing the fiber mat from the mandrel byrolling the fiber mat off of the end of the mandrel, wherein the fibermat forms a toroidal shaped structure once removed from the mandrel. 11.The method of claim 9, wherein the collector comprises the rotating drumor the flat plate, and wherein removing the fiber mat from the rotatingdrum or the flat plate produces at least one of a sheet of the nanofibermat or a roll of the nanofiber mat, that can be subsequently cut tosize, formed by rolling over a mandrel, and treated with heat to retainthe desired shape.
 12. The method of claim 6, wherein the heat treatmentoperation converts pre-ceramic nanofibers with an average diameter of100 nm or larger_into ceramic nanofibers with an average diameter of 50nm or larger.
 13. The method of claim 6, wherein removing the fiber matfrom the collector, to form the fiber mat into a shape, comprisesforming the fiber mat into a toroidal shape.
 14. The method of claim 13,wherein after performing the heat treatment operation, the ceramicstructure forms a ceramic mini-tube.
 15. The method of claim 14, whereinthe ceramic mini-tube has a diameter of about 1 mm-2 mm.
 16. The methodof claim 14, wherein the ceramic mini-tube has a length of at least 1.0mm.
 17. The method of claim 14, wherein the ceramic mini-tube has poresabout 1 μm in size.
 18. A method for making a ceramic mini-tubeconfigured for use in a fluid modification system, the methodcomprising: using an electrospinning system to receive a quantity ofprecursor solution; using the electrospinning system to create anelectric field which causes the precursor solution, when emitted, to bestretched into a fiber jet; depositing the fiber jet on a rotatingcollector resulting in a fiber mat; removing the fiber mat from thecollector, wherein the fiber mat is formed into a toroidal shape;further processing the fiber mat so that the fiber mat retains thetoroidal shape; and performing a heat treatment operation to convert thefiber mat into a ceramic mini-tube having the toroidal shape; andwherein the ceramic mini-tube comprises a diameter of at least about 1mm.
 19. The method of claim 18, wherein the depositing the fiber jet ona rotating collector comprises depositing the fiber jet on at least oneof: a rotating mandrel; or a rotating drum.
 20. The method of claim 18,wherein the ceramic mini-tube includes at least one of a diameter of 1mm-2 mm, or a length of at least 1 mm, or pores about 1 μm in size.